                The present invention relates to a method for immunologically measuring tumor-related antigen RCAS1 and kit for measuring the same, a method for immunologically measuring anti-RCAS1 antibody and a kit for measuring the same, and a method for immunologically measuring RCAS1 receptor.        
In the study of human tumors, there have been reported some tumor-related antigens such as CEA, CA19-9, α-fetoprotein and the like. In addition, monoclonal antibodies against these tumor-related antigens have been made and it has been showed that the detection of tumor-related antigens using these monoclonal antigens is effective for diagnosis of cancer. Further, as an application to the cancer treatment, there has been studied a method for specifically binding an anti-cancer agent or a radioactive substance to these monoclonal antibodies and, thereby, cancer cells are specifically attacked.
However, expression of the above tumor-related antigen is not uniform depending upon tissues and, in a sense that cancers are widely detected, it cannot be said that a method for treatment or a method for diagnosis utilizing the above monoclonal antibody against the tumor-related antigen is sufficient. Thus, there is desired the study of novel tumor-related antigens and antibodies against them.
Further, there are many kinds of cancers, for example, malignant cancers having the strong infiltrating property, cancers having relatively better prognosis, cancers having the high sensitivity to chemical therapy and the like. It is desired that a method for diagnosis and a method for treatment are provided depending upon the nature of these cancers. In particular, determination whether prognosis is better or not has the important meaning in the treatment of cancers.
On the other hand, uterine neck adenocarcinoma which occupies 5 to 20% of adenocarcinomas has been studied. Such the cancer is known to have the lower sensitivity to radiation therapy and chemical therapy as compared with uterine neck platycyte cancer. The development of a method of treating that cancer is of course desired and the study of biological property of the adenocarcinoma and the sensitivity to radiation and the like is considered to be highly valuable also in the development of anti-cancer agents and a method for diagnosis in the other cancers.
In order to examine the biological property of uterine neck adenocarcinoma and the sensitivity to anti-cancer agents, the present inventors established the SiSo cell strain and reported the properties thereof (International Journal of Oncology 6: 1099–1104, 1995 and Cancer vol. 77 1501–1509, 1996). In the study thereafter, a monoclonal antibody (22-1-1 monoclonal antibody) against the SiSo cell was made and, by utilizing this, distribution in the tissues and the biological property of an antigen which is recognized by 22-1-1 monoclonal antibody were studied. As a result, it was revealed that the antigen which is recognized by 22-1-1 monoclonal antibody is strongly expressed in uterine cancer and ovary cancer, particularly infiltrating cancer (Cancer vol. 77 1501–1509, 1996).
The present inventors revealed an antigen (RCAS1) on the cancer cell which is recognized by 22-1-1 monoclonal antibody and at the same time studied its properties. As a result, it was found that RCAS1 functions as a ligand for a receptor of immunological cells (T cell, B cell, NK cell and the like) and the possibility was suggested that RCAS1 may play an important role upon development by escaping the immunological surveillance mechanism, by inhibiting growth of immunological cells and inducing cell death due to apoptosis. In addition, the possibility that RCAS1 or anti-RCAS1 antibody is involved in immunological diseases, for example, autoimmune disease can be also considered.
As described above, RCAS1 or anti-RCAS1 antibody is an useful subject for the diagnosis of cancers and autoimmune diseases as well as the study of development and infiltration of tumors and it is considered that they are important for studying the mechanism of apoptosis. That is, since it is considered that measurement of RCAS1 and the like is effective for detecting cancers and presuming prognosis and establishing therapeutic strategy on diseases and contributes to the study of apoptosis, the development of simple and high accuracy method for quantitating RCAS1 and the like is desired. In addition, simple and high accuracy measurement of an expressed amount of RCAS1 receptor in immunological cells can be an useful means for clarifying the mechanism by which cancer cells escape immunological surveillance mechanism.